Antimony-free glass, antimony-free frit and a glass package that is hermetically sealed with the frit

ABSTRACT

An antimony-free glass suitable for use in a frit for producing a hermetically sealed glass package is described. The hermetically sealed glass package, such as an OLED display device, is manufactured by providing a first glass substrate plate and a second glass substrate plate and depositing the antimony-free frit onto the first substrate plate. OLEDs may be deposited on the second glass substrate plate. An irradiation source (e.g., laser, infrared light) is then used to heat the frit which melts and forms a hermetic seal that connects the first glass substrate plate to the second glass substrate plate and also protects the OLEDs. The antimony-free glass has excellent aqueous durability, good flow, low glass transition temperature and low coefficient of thermal expansion.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No.PCT/US2009/60962 filed on Oct. 16, 2009, which claims the benefit ofpriority to U.S. Provisional Application No. 61/106,730 filed on Oct.20, 2008, both applications being incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to an antimony-free glass, a fit madetherefrom, and a hermetically sealed glass packages sealed with the fritthat is suitable to protect thin film devices that are sensitive to theambient environment. Some examples of such devices are organic emittinglight diode (OLED) displays, sensors, photovoltaic and other opticaldevices. The present invention is demonstrated using OLED displays as anexample.

BACKGROUND

OLEDs have been the subject of a considerable amount of research inrecent years because of their use and potential use in a wide variety ofelectroluminescent devices, and are now reaching commercialization. Forinstance, a single OLED can be used in a discrete light emitting deviceor an array of OLEDs can be used in lighting applications or flat-paneldisplay applications (e.g., OLED displays). OLED displays are known asbeing very bright and having a good color contrast and wide viewingangle. However, OLED displays, and in particular the electrodes andorganic layers located therein, are susceptible to degradation resultingfrom interaction with oxygen and moisture leaking into the OLED displayfrom the ambient environment. It is well known that the life of the OLEDdisplay can be significantly increased if the electrodes and organiclayers within the OLED display are hermetically sealed from the ambientenvironment. Unfortunately, in the past it was very difficult to developa sealing process to hermetically seal the OLED display. Some of thefactors that made it difficult to properly seal the OLED display arebriefly mentioned below:

-   -   The hermetic seal should provide a barrier for oxygen (10⁻³        cc/m²/day) and water (10⁻⁶ g/m²/day).    -   The size of the hermetic seal should be minimal (e.g., <2 mm) so        it does not have an adverse effect on size of the OLED display.    -   The temperature generated during the sealing process should not        damage the materials (e.g., electrodes and organic layers)        within the OLED display. For instance, the first pixels of OLEDs        which are located about 1-2 mm from the seal in the OLED display        should not be heated to more than 100° C. during the sealing        process.    -   The gases released during the sealing process should not        contaminate the materials within the OLED display.    -   The hermetic seal should enable electrical connections (e.g.,        thin-film chromium) to enter the OLED display.

Today, one method for sealing the OLED display is to use different typesof epoxies, inorganic materials and/or organic materials that form theseal after they are cured by ultra-violet light. For example, some sealsuse a composite-based approach where alternate layers of inorganicmaterials and organic materials can be used to seal the OLED display.Although these types of seals usually provide good mechanical strength,they can be very expensive and there are many instances in which theyhave failed to prevent the diffusion of oxygen and moisture into theOLED display. Another common way for sealing the OLED display is toutilize metal welding or soldering. However, the resulting seal is notdurable in a wide range of temperatures because of the substantialdifferences between the coefficients of thermal expansions (CTEs) of theglass plates and metal in the OLED display.

More recently, glass-based fits have been used to seal glass substrateplates in a glass package that provides excellent hermeticity to theenclosed device. But many of these fits contain toxic elements, such asantimony, which pose environmental hazards. There is a need for aglass-based frit suitable for hermetically sealing glass packages, suchas electronic devices (e.g. for display-type applications), having a lowcoefficient of thermal expansion (CTE) that does not contain antimony.

SUMMARY

The present invention includes a hermetically sealed OLED display andmethod for manufacturing the hermetically sealed OLED display.Basically, the hermetically sealed OLED display is manufactured byproviding a first glass substrate plate and a second glass substrateplate and depositing a frit onto the second glass substrate plate. Anorganic material, such as those used in the manufacture of an OLED maybe deposited on the first substrate plate. An irradiation source (e.g.,laser, infrared light) is then used to heat the frit which melts andforms a hermetic seal that connects the first glass substrate plate tothe second glass substrate plate and also protects the OLEDs. The fritis and antimony-free glass that contains vanadium, and possibly a CTElowering filler, such that when the irradiation source heats the frit,it softens and forms a bond. This enables the frit to melt and form thehermetic seal while avoiding thermal damage to the OLEDs. Vanadiumphosphate fits, for example, have proven especially suitable for sealingglass packages of the type just described, and in particularantimony-containing vanadium phosphate frits. Such frits are verystable, exhibit high optical absorbance and have excellent mechanicaland aqueous durability. Unfortunately, antimony is a toxic element, andefforts have been directed toward finding a replacement for antimonythat does not detrimentally affect the other beneficial attributes ofthe frit.

To that end, the excellent aqueous durability performance of Sb-vanadiumphosphate frits was maintained without Sb₂O₃ by replacement of theantimony oxide by a combination of Fe₂O₃+TiO₂, along with a smalladdition of ZnO to maintain flow and glass transition temperature(T_(g)). The presence of Fe₂O₃ was found to have the greatest effect inimproving durability. However, it raised T_(g), thus degrading frit flowduring sealing. In addition, fits with high Fe₂O₃ levels (equal to orgreater than about 25 mole %) tended to be oxidatively unstable, withrepeat samples fired to the same schedule (425° in N₂) exhibitingdifferent colors (brown or black), with marked differences in the degreeof flow. Although TiO₂ alone actually degraded aqueous durability tosome extent, the combination of (Fe₂O₃+TiO₂) proved to be an idealcombination from the standpoint of obtaining laser-sealable frits withboth high aqueous durability and low T_(g) (≦400° C.).

Both lab bench tests exposing the glass to 90° C. distilled water aswell as 85° C./85% relative humidity (RH) environmental chamber testingof laser-sealed samples indicate that fits based on theFe₂O₃—TiO₂—ZnO—V₂O₅—P₂O₅ system are capable of forming a hermetic sealafter laser-sealing that will withstand high humidity conditions forextended times (≧1000 hrs). An unexpected result of the (Fe₂O₃+TiO₂)replacement of Sb₂O₃ was that the CTE of the base frit glass decreasedby approximately half (from 70-80×10⁻⁷/° C. to 35-45×10⁻⁷/° C.), withonly a minor increase in T_(g) (355° C. to 370° C.). Typically, lowT_(g) glasses and fits have CTE values in the range 100-150×10⁻⁷/° C.Frits with CTE values near 40×10⁻⁷/° C. have the potential, with theaddition of fillers such as β-eucryptite, of being able to seal fusedsilica and other low CTE substrates such as Kovar™

In one embodiment an antimony-free glass is disclosed comprising:

-   -   V₂O₅ (40-50 mole %)    -   P₂O₅ (≧20 mole % and <25 mole %)    -   ZnO (0-10 mole %)    -   Fe₂O₃ (>0 mole % and <25 mole %)    -   TiO₂ (>0% and <25 mole %); and        wherein TiO₂+Fe₂O₃ is in the range from 20 mole % to 35 mole %.

In another embodiment an antimony-free glass according to claim 1,comprising:

-   -   V₂O₅ (40-50 mole %)    -   P₂O₅ (≧20 mole % and <25 mole %)    -   ZnO (5-10 mole %)    -   Fe₂O₃ (>0 mole % and <25 mole %)    -   TiO₂ (>0% and <25 mole %); and        wherein TiO₂+Fe₂O₃ is in the range from 20 mole % to 35 mole %.

In still another embodiment, an antimony-free glass is described havingthe following composition:

-   -   V₂O₅ (40 mole %)    -   P₂O₅ (20 mole %)    -   ZnO (5 mole %)    -   Fe₂O₃ (>0 mole % and <25 mole %)    -   TiO₂ (>0 mole % and <25 mole %); and        wherein TiO₂+Fe₂O₃ is 35 mole %.

In another embodiment an antimony-free glass is disclosed comprising:

-   -   V₂O₅ (50 mole %)    -   P₂O₅ (20 mole %)    -   ZnO (10 mole %)    -   Fe₂O₃ (>10 mole % and ≦15 mole %)    -   TiO₂ (>5 mole % and ≦10 mole %); and        wherein TiO₂+Fe₂O₃ is 20 mole %.

The antimony-free glass preferably has a T_(g)≦400° C. and a CTE in therange from 35×10⁻⁷/° C. to 45×10⁻⁷/° C. The antimony-free glass may, forexample, comprise a glass frit and optionally a CTE lowering filler suchas beta eucryptite.

In still another embodiment, an antimony-free glass is describedconsisting of

-   -   V₂O₅ (40-50 mole %)    -   P₂O₅ (≧20 mole % and <25 mole %)    -   ZnO (0-10 mole %)    -   Fe₂O₃ (>0 mole % and ≦20 mole %)    -   TiO₂ (>0% and ≦20 mole %); and        wherein TiO₂+Fe₂O₃ is in the range from 20 mole % to 35 mole %.

In another embodiment, an antimony-free glass is disclosed comprising:

-   -   V₂O₅ (40-50 mole %)    -   P₂O₅ (≧20 mole % and <25 mole %)    -   ZnO (5-10 mole %)    -   Fe₂O₃ (>0 mole % and ≦20 mole %)    -   TiO₂ (>0% and ≦20 mole %); and        wherein TiO₂+Fe₂O₃ is in the range from 20 mole % to 35 mole %.

In yet another embodiment, a glass package is described comprising:

a first glass plate;

a second glass plate; and

a frit that connects the first glass plate to the second glass plate andforms an hermetic seal therebetween, the frit including an antimony-freeglass comprising:

-   -   V₂O₅ (40-50 mole %)    -   P₂O₅ (≧20 mole % and <25 mole %)    -   ZnO (0-10 mole %)    -   Fe₂O₃ (>0 mole % and <25 mole %)    -   TiO₂ (>0 mole % and <25 mole %); and        wherein TiO₂+Fe₂O₃ is in the range from 20 mole % to 35 mole %.

The antimony-free glass of the frit may instead comprise:

-   -   V₂O₅ (40 mole %)    -   P₂O₅ (20 mole %)    -   ZnO (5 mole %)    -   Fe₂O₃ (>0 mole % and <25 mole %)    -   TiO₂ (>0 mole % and <25 mole %); and        wherein TiO₂+Fe₂O₃ is 35 mole %.

In other embodiments, the antimony-free glass of the frit may comprise:

-   -   V₂O₅ (50 mole %)    -   P₂O₅ (20 mole %)    -   ZnO (10 mole %)    -   Fe₂O₃ (>10 mole % and ≦15 mole %)    -   TiO₂ (>5 mole % and ≦10 mole %); and        wherein TiO₂+Fe₂O₃ is 20 mole %.

In some embodiments, the antimony-free glass of the frit comprises:

-   -   V₂O₅ (40-50 mole %)    -   P₂O₅ (≧20 mole % and <25 mole %)    -   ZnO (5-10 mole %)    -   Fe₂O₃ (>0 mole % and <25 mole %)    -   TiO₂ (>0 mole % and <25 mole %); and        wherein TiO₂+Fe₂O₃ is in the range from 20 mole % to 35 mole %.

Preferably, the antimony-free glass comprising the frit has a Tg≦400° C.Preferably, the antimony-free glass of the frit has a CTE in the rangefrom 35×10⁻⁷/° C. to 45×10⁻⁷/° C. The frit may optionally comprise aCTE-lowering filler.

In some embodiments the glass package may further comprise an organicmaterial, such as an organic material comprising an organic lightemitting diode, disposed between the first and second glass plates.

The invention will be understood more easily and other objects,characteristics, details and advantages thereof will become more clearlyapparent in the course of the following explanatory description, whichis given, without in any way implying a limitation, with reference tothe attached Figures. It is intended that all such additional systems,methods, features and advantages be included within this description, bewithin the scope of the present invention, and be protected by theaccompanying claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional illustration of the sealing of an exemplaryOLED device using a frit according to embodiments of the presentinvention.

FIG. 2 is a plot of coefficient of thermal expansion (CTE) as a functionof the substitution of Fe₂O₃ for TiO₂ in an Sb-free frit according toembodiments of the present invention in mole % where Fe₂O₃+TiO₂ isbetween 20 mole % and 35 mole %.

FIG. 3 is a plot comparing CTE as a function of temperature for anSb-free frit according to embodiments of the present invention and anSb-containing frit under both heating and cooling conditions.

DETAILED DESCRIPTION

In the following detailed description, for purposes of explanation andnot limitation, example embodiments disclosing specific details are setforth to provide a thorough understanding of the present invention.However, it will be apparent to one having ordinary skill in the art,having had the benefit of the present disclosure, that the presentinvention may be practiced in other embodiments that depart from thespecific details disclosed herein. Moreover, descriptions of well-knowndevices, methods and materials may be omitted so as not to obscure thedescription of the present invention. Finally, wherever applicable, likereference numerals refer to like elements.

FIG. 1 depicts a cross-sectional side view illustrating the sealing ofthe basic components of a hermetically sealed OLED display 10. OLEDdisplay 10 includes a multilayer sandwich of a first glass substrateplate 12, one or more OLEDs 14, frit 16 and a second glass substrateplate 18. OLED display 10 comprises hermetic seal 18 formed from fit 16that protects OLEDs 14 located between the first glass substrate plate12 and the second glass substrate plate 18. Hermetic seal 20 istypically located around the perimeter of OLED display 10. OLEDs 14 arelocated within a perimeter of hermetic seal 20. The composition of frit16, and more particularly the composition of the glass of frit 16, aswell as how the hermetic seal 20 is formed from frit 16 is described ingreater detail below.

In one embodiment, first and second substrate plates 12 and 18 aretransparent glass plates. Frit 16 is deposited along the edges of secondglass substrate plate 18. For instance, frit 16 can be placedapproximately 1 mm away from the free edges of the second glasssubstrate plate 18. In the preferred embodiment, frit 16 is a lowtemperature antimony-free glass frit containing vanadium to enhance theoptical absorbance of the frit. Frit 16 may also include a filler, sucha beta eucryptite, that lowers the coefficient of thermal expansion(CTE) of the frit so that it matches or substantially matches the CTEsof the two glass substrate plates 12 and 18.

OLEDs 14 and other circuitry are deposited onto second glass substrateplate 18. The typical OLED 14 includes an anode electrode, one or moreorganic layers and a cathode electrode. However, it should be readilyappreciated that other environmentally sensitive components can bedeposited onto second glass substrate plate 18.

Optionally, frit 16 can be pre-sintered to first glass substrate plate12 prior to sealing glass substrates 12 and 18 together. To accomplishthis, first substrate plate 12 comprising frit 16 deposited thereon isheated in a furnace or oven so that it becomes attached to the firstglass substrate plate 12.

Next, first and second glass substrate plates 12 and 18 are broughttogether with frit 16 and one or more OLEDs positioned between them, andfrit 16 is irradiated by irradiation source 22 (e.g. a laser or aninfrared lamp) so that the frit 16 forms hermetic seal 20 that connectsand bonds the first substrate plate 12 to second substrate plate 18.Hermetic seal 18 also protects OLEDs 14 by preventing oxygen andmoisture in the ambient environment from entering into the OLED display10.

It should be readily appreciated that the irradiating wavelength shouldbe within the band of high absorption in the particular frit 16. Forinstance, Ytterbium (900 nm<λ<1200 nm), Nd:YAG=1064 nm), Nd:YALO (λ=1.08μm), and erbium (λ≈1.5 μm) CW lasers can be used depending on theoptical properties of the particular frit 16 and glass substrate plates12 and 18.

It should be noted that most traditional low temperature sealing fitsare PbO-based, because PbO fits have good flow, and adhesion properties.However, the antimony-free frits disclosed herein not only have a lowerCTE than PbO-based fits, but also possess better aqueous durability, aswell as being comparable to the traditional Pb-based frits with respectto adhesion.

In addition, although the role played by P₂O₅ in a successful sealingfit is important, since it permits stable glasses to be formed, from alaser-sealing and post-seal performance standpoint the effect of Sb₂O₃and V₂O₅ should not be ignored. In previous testing, seals made withSb-free, Zn-based vanadium-phosphate frits could only survive therelatively benign environment of 60° C./40% RH, while seals made frommixed Sb—Zn vanadium phosphate fits survived 60° C./85% RH beforefailing. Conversely, only seals made with Sb-vanadium-phosphate fitssurvived 85° C./85% RH exposure. However, despite the role that Sb₂O₃plays in improving aqueous durability, feedback from potential customersconsistently raise concerns about its presence. Thus, recent emphasishas been placed on development of a glass suitable for a sealing fritthat is environmentally friendly, noting that antimony is a toxicelement.

Work on Sb₂O₃-free compositions began by first expressing a basic OLEDdevice sealing frit composition as a three component system (20 mole %Sb₂O₃—50 mole % V₂O₅—30 mole % P₂O₅), simplifying the composition to atwo component Sb₂O₃-free system (either 50 mole % V₂O₅—30 P₂O₅, 45 mole% V₂O₅—30 mole % P₂O₅, or 40 mole % V₂O₅—20 mole % P₂O₅), and thenidentifying the remaining components from the standpoint of their effecton aqueous durability, flow, glass transition temperature (T_(g)), andlaser-sealability. Both aqueous durability, laser-sealability, and flowof any candidate frit compositions needed to be comparable to theSb₂O₃-containing control sample, while the Tg requirements were relaxedwith the criterion that T_(g) had to be equal to or less than 400° C.(Frits with T_(g)>400° are unlikely to flow sufficiently during thepresintering step for OLED frits to be handleable in subsequentprocessing.) The following oxides were investigated as potentialsubstitutes for antimony (Sb₂O₃): WO₃, MoO₃, TeO₂, Bi₂O₃, Fe₂O₃, andTiO₂. ZnO was also investigated, although in view of the poor durabilityresults obtained for a ZnO—V₂O₅—P₂O₅ frit, it was considered only as aminor component (5-10%) to lower T_(g) and maintain flow. The variousoxides selected were chosen on the basis that they formed stable binaryglasses with V₂O₅.

All of the compositions investigated were melted, poured as glasspatties, then ball-milled to form fine-particle frits (typically with ad₅₀=3-5 μm). A key bench test to screen the different compositions wasto prepare and fire flow buttons of the various fits, and then to assesstheir aqueous durability. The flow buttons were fired in N₂ to 400-450°C. (depending upon T_(g) and crystallization tendency). After firing,the flow buttons were immersed in 90° C. de-ionized water for 48 hoursto assess their aqueous durability. Control samples of the OLED frit(either as the D1 base glass, or as a 70:30 blend of the base glass witha β-eucryptite filler) were also included in each evaluation. Of thepotential replacements for Sb₂O₃ that were investigated (see above),only TiO₂ and Fe₂O₃ appeared promising.

Listed in Tables 1 and 2 are results for a 50 mole % V₂O₅—30 mole % P₂O₅composition series with WO₃, MoO₃, WO₃+ZnO, Bi₂O₃, and TeO₂ as the thirdcomponent. Also shown are data on the standard OLED base glass, D1, as acomparison standard. All compositions (given in mole %) were evaluatedfor quality of glass formed from the pour, glass transition temperature(T_(g)) by DSC, flow and sinterability as a 3 μm powder hand-pressedinto a pellet (“flow button”) and fired at 400° C. for 1 hour in N₂, andaqueous durability (as gauged by the color of the supernatant for afired flow button sample—the darker the color, the less durable thesample) in the bench aqueous durability test described above. Note thatnone of the potential Sb₂O₃ replacements listed in Tables 1 and 2produced the acceptable level of glass quality, T_(g), flow, and aqueousdurability exhibited by the Sb₂O₃-containing control (as judged by theappearance of the supernatant after 48 hrs, 90° C. de-ionized H₂O).

TABLE 1 D1 (control) D2 D3 Composition Sb₂O₃, 22.9 V₂O₅, 50 V₂O₅, 50(molar basis) V₂O₅, 46.4 P₂O₅, 30 P₂O₅, 30 P₂O₅, 26.3 WO₃, 20 MoO₃, 20Fe₂O₃, 2.4 Al₂O₃, 1.0 TiO₂, 1.0 Glass quality at Excellent Fluid, goodVery fluid, good pour quality quality T_(g) 355° C. 349° C. 315° C. Flow(400°-1 hr, Very good flow Semi-glossy, Glossy and black N₂) andsinterability well-sintered, with some slump no flow Aqueous V. slightlytinted Black Black durability, appearance of supernatant (48 hrs, 90° C.D.I. H₂O)

TABLE 2 D4 D5 D6 Composition V₂O₅, 50 V₂O₅, 50 V₂O₅, 50 (molar basis)P₂O₅, 30 P₂O₅, 30 P₂O₅, 30 WO₃, 10 Bi₂O₃, 20 TeO₂, 20 ZnO, 10 Glassquality at Good glass, Crystallized More viscous pour fluid, after pour,glass poured well pouring looked good T_(g) 323° C. Not eval. 329° C.Flow (400° C.-1 hr, Poor flow Not eval. Semi-glossy black, N₂) no slumpAqueous Black Not eval. Black durability

More positive results for Sb₂O₃-free vanadium phosphate frits wereobtained by Fe₂O₃ and/or TiO₂ replacement of Sb₂O₃ (see Tables 3 and 4).All compositions are expressed in mole %. Several combinations ofFe₂O₃+TiO₂ produced good glasses at pouring. High TiO₂ glasses (i.e.,≧25%) such as D8 had acceptable T_(g) and flow properties, but alsoexhibited poor aqueous durabilities. Higher Fe₂O₃ glasses (i.e., ≧25 or30%) such as D7 and D11 tended to produce poor glasses at pour, asevidenced by substantial surface devitrification. The relatively poorstability of these glasses (as indicated by the high amount of surfacedevitrification formed in the patty at pouring) resulted in poor flow asfrits. They also tended to be unstable with respect to oxidation state,with a fired flow button from the same lot of powder alternatelyappearing either black (reduced) or red (oxidized) after the same firingconditions. Also included in Table 4 is D14, a glass with relativelyhigh Fe₂O₃ and TiO₂ levels, but with 10 mole % ZnO to lower the expectedincrease in T_(g) from the Fe₂O₃. Note that a second approach toaccommodating high Fe₂O₃ levels is increasing the V₂O₅ content. But asmay be seen for D9 and D10, aqueous durability was compromised at higherV₂O₅ content.

TABLE 3 D7 D8 D9 D10 Composition V₂O₅, 45 V₂O₅, 45 V₂O₅, 50 V₂O₅, 50(molar basis) P₂O₅, 30 P₂O₅, 30 P₂O₅, 30 P₂O₅, 30 Fe₂O₃, 25 TiO₂, 25TiO₂, 15 TiO₂, 10 Fe₂O₃, 5 Fe₂O₃, 10 Glass quality Substantial PouredPoured Poured at pour surface devit nicely nicely nicely T_(g) 353° 345°323° 322° Flow (400° C., Poorly sintered Semi-glossy Sintered, Sintered,1 hr, N₂) black, some flow slight flow no slump Aqueous Not tested BlackMed. green Med. durability, green appearance of supernatant (48 hrs, 90°C. D.I. H₂O)

TABLE 4 D11 D12 D13 D14 Composition V₂O₅, 42 V₂O₅, 40 V₂O₅, 45 V₂O₅, 40(molar basis) P₂O₅, 28 P₂O₅, 25 P₂O₅, 25 P₂O₅, 20 TiO₂, 0 TiO₂, 17.5TiO₂, 0 TiO₂, 15 Fe₂O₃, 30 Fe₂O₃, 17.5 Fe₂O₃, 30 Fe₂O₃, 15 ZnO, 10 Glassquality Viscous, Good glass, Viscous, Good glass, at pour surface devitno devit surface no devit devit T_(g) 371° 364° 376° 360° Flow (400° C.,Poor - Poor - Poor Semi-glossy 1 hr, N₂) powdery and powdery black,unconsolidated sintered, no slump Aqueous Not eval. Not eval. Not eval.Lt. brown durability

It should also be noted that although the test samples of Tables 3 and 4having P₂O₅ levels equal to or greater than 25 mole percent performedpoorly, it is anticipated that P₂O₅ levels less than 25 mole % can besuccessfully employed. Table 5 summarizes the results of a second set ofFe₂O₃ and TiO₂ melts at 10% ZnO. All compositions are expressed in mole%. As for the initial series, some combination of Fe₂O₃ and TiO₂ ispreferred, since Fe₂O₃ contributes excellent aqueous durability (but atthe cost of high T_(g) and reduced frit sintering at 400°), and TiO₂results in lower T_(g) and improved flow (but at the cost of aqueousdurability).

TABLE 5 D15 D16 D17 D18 D19 Composition V₂O₅, 50 V₂O₅, 50 V₂O₅, 50 V₂O₅,50 V₂O₅, 50 (molar basis) P₂O₅, 20 P₂O₅, 20 P₂O₅, 20 P₂O₅, 20 P₂O₅, 20ZnO, 10 ZnO, 10 ZnO, 10 ZnO, 10 ZnO, 10 Fe₂O₃, 0 Fe₂O₃, 5 Fe₂O₃, 10Fe₂O₃, 15 Fe₂O₃, 20 TiO₂, 20 TiO₂, 15 TiO₂, 10 TiO₂, 5 TiO₂, 0 Glassquality at Poured nicely Poured Poured Poured Poured pour nicely nicelynicely nicely T_(g) 297° 310° 322° 333° 348° Flow (400°-1 hr,Well-sintered, Well- Sintered, Sintered, Sintered, N₂) good flowsintered, slight flow some flow little flow good flow Aqueous durabilityDark black Dark black Dark black Clear Clear

An additional series of melts were made at higher levels of [Fe₂O₃+TiO₂]with ZnO maintained at 5 mole % (see Tables 6 and 7 below). Allcompositions are expressed in mole %. Note that to accommodate thehigher T_(g) of the high Fe₂O₃ glasses, flow was evaluated at 425° C.,rather than the 400° C. previously used.

TABLE 6 D20 D21 D22 D23 Composition V₂O₅, 40 V₂O₅, 40 V₂O₅, 40 V₂O₅, 40(molar basis) P₂O₅, 20 P₂O₅, 20 P₂O₅, 20 P₂O₅, 20 ZnO, 5 ZnO, 5 ZnO, 5ZnO, 5 Fe₂O₃, 35 Fe₂O₃, 30 Fe₂O₃, 25 Fe₂O₃, 20 TiO₂, 0 TiO₂, 5 TiO₂, 10TiO₂, 15 Glass quality Substantial surface + Surface devit Surface devitGood glass, no at pour bulk devit devit T_(g) 416° 407° 400° 389° Flow(425°- Not sinterable at Not sinterable at Not sinterable at Sintered,no 1 hr, N₂) 425° 425° 425° flow Aq. durability Not tested Not testedNot tested Clear

TABLE 7 D24 D25 D26 D27 D28 Composition V₂O₅, 40 V₂O₅, 40 V₂O₅, 40 V₂O₅,40 V₂O₅, 40 (molar basis) P₂O₅, 20 P₂O₅, 20 P₂O₅, 20 P₂O₅, 20 P₂O₅, 20ZnO, 5 ZnO, 5 ZnO, 5 ZnO, 5 ZnO, 5 Fe₂O₃, 17.5 Fe₂O₃, 15 Fe₂O₃, 10Fe₂O₃, 5 Fe₂O₃, 0 TiO₂, 17.5 TiO₂, 20 TiO₂, 25 TiO₂, 30 TiO₂, 35 Glassquality Good glass, Good glass, Good glass, Good glass, no Good glass,no at pour no devit no devit no devit devit devit T_(g) 379° 367° 351°333° 324° Flow (425°- Sintered, Sintered Sintered, Sintered, mod.Sintered, good 1 hr, N₂) slight flow slight flow mod. flow flow flow Aq.Clear with v. Clear Med. green Med. green Med. green durability slighttint (residue) (residue)

As seen in previous results from Tables 1, 2 and 3, 4, Fe₂O₃ levels notmuch higher than 20 mole % (e.g. about 25 mole %) resulted in fits withhigh T_(g), poor stability, and unacceptable flow during 400-425°sintering. Similarly, TiO₂ not much higher than 20 mole % (e.g. about25%), resulted in fits with acceptable T_(g), flow, and stability, butwith unacceptable aqueous durability. Frits with Fe₂O₃ levels rangingbetween from about 10 to less than 25 mole %, and with TiO₂ levels fromabout 15 to less than 25 mole % (at 5-10 mole % ZnO) combine excellentaqueous durability with acceptable flow, T_(g), and glass stability.

The aqueous durability of the (Fe₂O₃+TiO₂+ZnO) Sb₂O₃-free V₂O₅—P₂O₅ fitswere found to be comparable to or slightly superior to theSb₂O₃-containing standard composition. An unexpected result of theSb₂O₃-free work is that the coefficient of thermal expansion (CTE)becomes dramatically lower for the (Fe₂O₃+TiO₂+ZnO) fits at higher Fe₂O₃levels. Shown below in FIG. 2 are CTE data for sintered fits whosecomposition is listed in Tables 3, 4 and 5. Data are presented for allsinterable fits in the 20 mole % (Fe₂O₃+TiO₂) series of Table 3, 4,(curve 120) and for the 35 mole % (Fe₂O₃+TiO₂) series of Table 5 (curve122). CTE data for sintered frit bars are plotted as a function of Fe₂O₃level in each series up to 20 mole % Fe₂O₃, the apparent upper limit toachieving frits with good sinterability and oxidative stability. Notethat CTE values are highest at 0 mole % Fe₂O₃/maximum TiO₂ (20 and 35mole %, respectively), become essentially constant with increasing Fe₂O₃level at 60-65×10⁷/° C., and then decrease substantially at Fe₂O₃>15mole % (5 mole % and 20 mole % TiO₂, respectively), reaching a value ofapproximately 40×10⁻7/° C. at 17.5-20 mole % Fe₂O₃. By comparison, theCTE of the Sb₂O₃-containing base frit is approximately 70-80×10⁻⁷/° C.

A more direct comparison of CTE between the Sb₂O₃-containing andSb₂O₃-free frits is shown in FIG. 3 where CTE curves are plotted for D1under both heating and cooling conditions (curves 124 and 126,respectively) and D29 (remelt of D24, Table 7) also under both heatingand cooling conditions (curves 128 and 130, respectively). With a CTEvalue of approximately 40×10⁻⁷/° C. for an unfilled frit, it ispossible, with the addition of fillers such as β-eucryptite, to lowerthe CTE value of this frit close to that of fused silica.

The lab scale aqueous durability results for Sb-free frits werecorroborated in a large scale sealing trial involving 85° C./85% RHexposure of laser-sealed samples. Shown in Table 8 are results of thetrial and comparison between the standard OLED frit (D1, Table 1; usedas a 70:30 blend with low CTE filler β-eucryptite), and an Sb-free frit(D29, remelt of D24, Table 7; used as an 80:20 wt. blend with low CTEfiller β-quartz). Each frit blend was made into a paste, dispensed onseveral sheets of EAGLE^(XG) display glass, presintered (Sb-containingstandard, 325°-2 hr, air+400°−1 hr N₂; Sb-free, 325°−2 hr, air+425°−1 hrN₂), sealed to sheets of EAGLE^(XG), placed in an 85° C./85% relativehumidity environmental chamber, and then examined periodically forevidence of seal leakage and Ca metal breakdown. In total, there were 3sheets of the Sb-containing control composition and 7 sheets of theantimony-free composition included in the study, with 9 sealed arrays ofCa metal tabs per sheet. As may be seen in Table 8, several arraysfailed either immediately after sealing or within 100 hrs of placingthem in 85° C./85% RH chamber for both the Sb-control and the Sb-freefrits; these failures were related, most likely, to gross defects suchas contamination present at random for each frit. However, after 96 hrs,no additional failures were observed for either the Sb-control or theSb-free frit seals.

TABLE 8 No. of good cells At After After Laser- start of 96 hrs of 1056hrs sealed 85/85 85/85 of 85/85 Standard Sb-frit blend (70:30, 27 (3 2524 24 D1:β-eucryptite) sheets) Sb-free frit blend (80:20, 63 (7 61 57 57D29:β-quartz) sheets)

In summary, the excellent aqueous durability performance of Sb-vanadiumphosphate fits was maintained without Sb₂O₃ by replacing the antimonyoxide with a combination of Fe₂O₃+TiO₂, along with a small addition ofZnO to maintain flow and glass transition temperature (T_(g)). Thepresence of Fe₂O₃ was found to have the greatest effect in improvingdurability. However, in large amounts it raised T_(g), thus degradingfrit flow during sealing. In addition, frits with high Fe₂O₃ levels(equal to or greater than about 25 mole %) tended to be oxidativelyunstable, with repeat samples fired to the same schedule (425° in N₂)exhibiting different colors (brown or black), with marked differences inthe degree of flow. Although TiO₂ actually degraded aqueous durabilityto some extent when added by itself, the combination of (Fe₂O₃+TiO₂)appeared to be an ideal combination from the standpoint of obtaininglaser-sealable fits with both high aqueous durability and low T_(g)(≦400°).

Both lab bench tests in 90° C. distilled water as well as 85° C./85%relative humidity (RH) environmental chamber testing of laser-sealedsamples indicate that fits based on the Fe₂O₃—TiO₂—ZnO-V₂O₃—P₂O₃ systemare capable of forming a hermetic seal after laser-sealing that willwithstand high humidity conditions for extended times (≧1000 hrs). Anunexpected result of the (Fe₂O₃+TiO₂) replacement of Sb₂O₃ was that theCTE of the Sb-free frit without fillers decreased by approximately half(from 70-80×10⁴/° C. to 35-45×10⁻⁷/° C.), with only a minor increase inT_(g) (from 355° C. to 370° C.). Frits with CTE values near 40×10⁻⁷/° C.have the potential, with the addition of fillers such as β-eucryptite,of being able to seal fused silica and other low CTE substrates such asKovar™.

Although several embodiments of the present invention has beenillustrated in the accompanying Drawings and described in the foregoingDetailed Description, it should be understood that the invention is notlimited to the embodiments disclosed, but is capable of numerousrearrangements, modifications and substitutions without departing fromthe spirit of the invention as set forth and defined by the followingclaims.

1. An antimony-free glass comprising: V₂O₅ (40-50 mole %) P₂O₅ (≧20 mole% and <25 mole %) ZnO (0-10 mole %) Fe₂O₃ (>0 mole % and <25 mole %)TiO₂ (>0 mole % and <25 mole %); and wherein TiO₂+Fe₂O₃ is in the rangefrom 20 mole % to 35 mole %.
 2. The antimony-free glass according toclaim 1, comprising: V₂O₅ (40-50 mole %) P₂O₅ (≧20 mole % and <25 mole%) ZnO (5-10 mole %) Fe₂O₃ (>0 mole % and <25 mole %) TiO₂ (>0 mole %and <25 mole %); and wherein TiO₂+Fe₂O₃ is in the range from 20 mole %to 35 mole %.
 3. The antimony-free glass according to claim 1, whereinthe antimony-free glass has the following composition: V₂O₅ (40 mole %)P₂O₅ (20 mole %) ZnO (5 mole %) Fe₂O₃ (>0 mole % and <25 mole %) TiO₂(>0 mole % and <25 mole %); and wherein TiO₂+Fe₂O₃ is 35 mole %.
 4. Theantimony-free glass according to claim 1, wherein the glass has thefollowing composition: V₂O₅ (50 mole %) P₂O₅ (20 mole %) ZnO (10 mole %)Fe₂O₃ (>10 mole % and <15 mole %) TiO₂ (>5 mole % and <10 mole %); andwherein TiO₂+Fe₂O₃ is 20 mole %.
 5. The antimony-free glass according toclaim 1, wherein the antimony-free glass has a T_(g)≦400° C.
 6. Theantimony-free glass according to claim 1, wherein the antimony-freeglass has a CTE in the range from 35×10⁻⁷/° C. to 45×10⁷/° C.
 7. Theantimony-free glass according to claim 1, wherein the antimony-freeglass comprises a glass frit.
 8. The antimony-free glass according toclaim 7, wherein the glass fit further comprises a CTE lowering filler.9. An antimony-free glass consisting of: V₂O₅ (40-50 mole %) P₂O₅ (≧20mole % and <25 mole %) ZnO (0-10 mole %) Fe₂O₃ (>0 mole % and ≦20 mole%) TiO₂ (>0 mole % and ≦20 mole %); and wherein TiO₂+Fe₂O₃ is in therange from 20 mole % to 35 mole %.
 10. The antimony-free glass accordingto claim 9, wherein: V₂O₅ (40-50 mole %) P₂O₅ (≧20 mole % and <25 mole%) ZnO (5-10 mole %) Fe₂O₃ (>0 mole % and ≦20 mole %) TiO₂ (>0 mole %and ≦20 mole %); and wherein TiO₂+Fe₂O₃ is in the range from 20 mole %to 35 mole %.
 11. A glass package comprising: a first glass plate; asecond glass plate; and a frit that connects the first glass plate tothe second glass plate and forms an hermetic seal therebetween, the fritincluding an antimony-free glass comprising: V₂O₅ (40-50 mole %) P₂O₅(≧20 mole % and <25 mole %) ZnO (0-10 mole %) Fe₂O₃ (>0 mole % and <25mole %) TiO₂ (>0 mole % and <25 mole %); and wherein TiO₂+Fe₂O₃ is inthe range from 20 mole % to 35 mole %.
 12. The glass package accordingto claim 11, wherein the antimony-free glass comprises: V₂O₅ (40 mole %)P₂O₅ (20 mole %) ZnO (5 mole %) Fe₂O₃ (>0 mole % and <25 mole %) TiO₂(>0 mole % and <25 mole %); and wherein TiO₂+Fe₂O₃ is 35 mole %.
 13. Theglass package according to claim 11, wherein the antimony-free glasscomprises: V₂O₅ (50 mole %) P₂O₅ (20 mole %) ZnO (10 mole %) Fe₂O₃ (>10mole % and <15 mole %) TiO₂ (>5 mole % and <10 mole %); and whereinTiO₂+Fe₂O₃ is 20 mole %.
 14. The glass package according to claim 11,wherein the antimony-free glass comprises: V₂O₅ (40-50 mole %) P₂O₅ (≧20mole % and <25 mole %) ZnO (5-10 mole %) Fe₂O₃ (>0 mole % and <25 mole%) TiO₂ (>0 mole % and <25 mole %); and wherein TiO₂+Fe₂O₃ is in therange from 20 mole % to 35 mole %.
 15. The glass package according toclaim 11, wherein the antimony-free glass has a Tg≦400° C.
 16. The glasspackage according to claim 11, wherein the antimony-free glass has a CTEin the range from 35×10⁻⁷/° C. to 45×10⁻⁷/° C.
 17. The glass packageaccording to claim 11, wherein the frit comprises a CTE-lowering filler.18. The glass package according to claim 11, further comprising anorganic material disposed between the first and second glass plates. 19.The glass package according to claim 11, wherein the organic materialcomprises an organic light emitting diode.